Loss of protistan diversity weakens soil phosphorus availability

Plants and their associated microbiomes symbiotically regulate the phosphorus(P) availability in rhizosphere soils. However, the impact of protists, a regulator of other microbes (bacteria and fungi) in the soil food webs, on soil P availability is not well-known. we simulate biodiversity loss using dilution-to-extinction method and explore its effects on P availability through a greenhouse experiment. Additionally, we investigate the implications for soil P availability. We noted a substantial reduction in protistan diversity in the diluted treatment relative to the undiluted one, with a peak decrease of 74.5 %. The protistan alpha diversity showed a significant positive correlation with available phosphorus (AP) content and phosphatase (PHOS) activity, suggesting that protistan diversity influences P availability. Additionally, Linear regression analysis revealed that the size and stability of the protistan co-occurrence network were significantly positively correlated with soil AP and PHOS, indicating that the reduction in protistan interactions weakened soil P availability under wheat cultivation. Structural equation model and random forest modeling analysis indicated that protistan network interactions and diversity are the major predictors of AP content and PHOS activity. Dilution modulated the relationship between protistan community and soil P availability. Our findings suggest that the protistan community plays a crucial role in maintaining soil P availability, particularly in monoculture agricultural systems. The study highlights the importance of considering the impacts of protistan diversity loss on ecosystem functions, especially in the context of intensive agricultural practices and climate change.